Abstract
In this dissertation, the maximum amplitude of transient response at terminals of a piezoelectric vibrator and its drive conditions, induced immediately after an AC voltage connected to the vibrator is switched off, are first studied. Then, parameters associated with losses of the vibrator are determined by transient response at the terminals, and the losses are also. Moreover, characteristics of the vibrator, including resonant frequency, parameters associated with the losses and the losses, affected by motional current of the vibrator are researched. To do so, an equivalent circuit of the vibrator is first expressed to derive steady-state responses and transient response at the terminals of the vibrator driven by sinusoidal wave voltage. Meanwhile, the transient response is associated with initial states of the vibrator, and the maximum amplitude of the transient response depends on frequency and switching-off time of the voltage. Then, according to measured oscillated frequency of the transient response and measured resonant frequencies of the vibrator, L-C parameters of the equivalent circuit are almost constant, and thus parameters associated with the losses are estimated using AC and DC time constants of the transient response. Experimental results indicate that the estimation method applied to determine parameters associate with the losses is easy and practical. Moreover, a parallel resistor is connected to the vibrator to reduce DC transient response time of the transient response and shorten the time of the hurt for users or the damage for instruments, and the steady-state responses by the parallel resistor are unaffected. Finally, both an ultrasonic levitation system and a piezoelectric actuating clutch system are driven using the vibrator, and measured when mechanisms and drive circuits of them are designed and fabricated.